High performance portable computers commonly include a primary or main battery for operating the computer when it is not plugged into an ac power supply. The type of battery selected is dependent upon size, weight, and power requirements and is preferably rechargeable. While there are many battery operated computers available in different sizes ranging from desktop models, to laptops, handheld, and pocket models, the invention is designed for use primarily in high performance systems such as is currently available in many commercially available laptop models. Generally, most such computers have very simplistic battery charge monitors. Many provide only low battery warning signals allowing the user to save any volatile data on a disk, before the computer is shut off.